This application is based on an application No. 11-47550 filed in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a bone mill for crushing, into particles having the desired size, a bone (human bone) taken out from a living body at its suitable part.
Bone particles obtained by crushing a bone with a bone mill, are used as a spacer or the like for an artificial bone filled in the prosthesis part of the living body.
2. Description of Related Art
In vertebrate animals, the bones serve as a form element which constitutes the framework. In particular, the human bones are arranged to take physical exercise together with the muscles, and serve as the foundation of a variety of parts of the human body. Further, the human bones are important organs for maintaining the body form and the like.
A human bone is structurally provided on the surface thereof with the white periosteum. The periosteum through which nerves and blood vessels pass, is related to nutrition intake and growth. On the other hand, it is known that the outer layer of a bone is hard because it is made of tight matter (hard matter), and that the inner layer is spongy and porous.
Technology in the surgical medicare field has made rapid progress. In particular, artificial living-body materials, prosthetic tools and the like are always improved in performance, and a large number of persons share in the benefit.
The artificial living-body materials of prior art are neither poisonous nor stimulative to a living body, but most of them have no biological affinity. Accordingly, when bone cement is used for fixing a prosthetic tool to the bone or for filling the gap between a prosthetic tool and the bone, this involves the likelihood that the heat of polymerization of the bone cement exerts an adverse effect on the living body, or that due to changes with the passage of time, the bone cement is loosened to deteriorate the safety.
In view of the foregoing, a bone taken out from a living body at its suitable part has conventionally been crushed into particles having the desired size (e.g., 4 mm2xcx9c10 mm2), and the bone particles thus crushed have been used as a spacer or filler for filling the gap between the prosthesis tool and the bone. According to this method, such a spacer or filler has an affinity to the bone because human bone is used. Thus, this method has no concern for adverse effect of the heat of polymerization to the living body and for the looseness due to changes with the passage of time.
To crush a bone taken out from a living body into fine bone particles, it is required to crush the bone with a hammer or an edged tool. This disadvantageously requires working skill and time. In particular, the bone taken from a living body is excellent in tenacity, but hard. Further, blood vessels and a variety of nerves are contained in the surface periosteum. It is therefore difficult to crush the bone. Further, the crushed bone particles are disadvantageously not uniform.
In view of the foregoing, a variety of bone mills are produced and commercially available. FIG. 1 shows an example of the commercially available bone mills. To crush a bone with this bone mill, the bone is previously treated. More specifically, the bone taken from a living body is cut into pieces of about 3 cm2 with a bone saw or the like. A cut bone piece is inserted into an inlet port (which is disposed at a pushing-out portion such as a syringe) of the bone mill in FIG. 1. Then, the inserted bone is pushed in with one hand, and a switch for reciprocating a blade arranged to cut the bone, is pressed with the other hand. This causes nitrogen gas to be blown out to operate the blade.
This bone mill requires a previous treatment of cutting a bone into pieces having a predetermined size. Further, the size of crushed bone particles varies with the manner in which the bone mill is operated. Thus, it takes time before the operator is used to the bone mill. Further, bone crushing takes as much as 3xcx9c5 minutes.
According to another example of the commercially available bone mills, projecting blades are disposed on a shaft of rotation, and a bone is pushed to these rotational blades such that the bone is scraped off.
In the bone mill having the arrangement above-mentioned, the bone should always be pressed with the hand. This disadvantageously gives trouble. Further, bone crushing takes at least about 5 minutes.
In view of the foregoing, the present invention is proposed with the main object of providing a bone mill having a novel mechanism capable of crushing a bone into particles having the desired size in a short period of time.
It is another object of the present invention to provide a bone mill easy to handle and operate.
It is a further object of the present invention to provide a bone mill capable of crushing a bone without any loss.
It is still another object of the present invention to provide a bone mill which can readily be cleaned and sterilized after used.
A bone mill according to the present invention has a pair of first cutter unit and second cutter unit. A bone to be crushed is taken in between the first cutter unit and the second cutter unit. While passing between the first cutter unit and the second cutter unit, the bone is crushed.
Each cutter unit has a plurality of disks disposed in parallel to one another at regular intervals. Each disk is provided on the periphery thereof with a blade for crushing a bone. The cutter units are positioned such that the disks of the first cutter unit are fitted in the gaps between adjacent disks of the second cutter unit. Both the disks of the first cutter unit and the disks of the second cutter unit are mutually inwardly rotated. Accordingly, when a bone to be crushed is supplied between the cutter units, the bone is taken in by and between the disks of the first cutter unit and the disks of the second cutter unit, both disks being mutually inwardly rotated. Thus, the blades of the disks bite the bone, causing the same to be broken. While passing between the disks of the first cutter unit and the disks of the second cutter unit, the bone is crushed by these disks so positioned as to be fitted in each other.
Preferably, each of the first and second cutter units has small-diameter disks and large-diameter disks such that a bone to be crushed is readily taken in. The blades formed on the large-diameter disks readily take in a bone to be crushed, while the blades formed on the small-diameter disks readily crush the bone.
These and other features, objects and advantages of the present invention will be more fully apparent from the following detailed description set forth below when taken in conjunction with the accompanying drawings.